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 May 3 answered Converting recurrence into matrix May 3 answered Suppose that a function $f$ defined on $\mathbb R^2$ satisfies the following conditions : May 3 comment Any finite index subgroup of $\mathbb Z_p$ is open @Donkey_2009 Rewritten accordingly, I hope May 3 revised Any finite index subgroup of $\mathbb Z_p$ is open added 301 characters in body May 3 comment Sums of two irreducible polynomials over $\mathbb{Z}$ @KCd I could not because I didn't know that. This proof was just the first that came to my mind. - Actually, the link in the answer here is dead and it appears from what Dietrich Bured wrote there, that Hayes did a little better by keeping degree $n$ whereas I took the freedom to increase the degree (which maybe makes the argument simpler and allows to catch the degree $0$ case) May 3 comment Circle from three points on surface of sphere I'd still (out of lazyness) switch to 3d cartesian coordinates and intersect the plane of the three points with the sphere ... May 3 awarded Nice Answer May 3 answered Sequences: $\frac{|x_n|}{1+|x_n|}\to0$ implies $x_n\to0$? May 3 answered Sums of two irreducible polynomials over $\mathbb{Z}$ May 3 reviewed Reopen Proving that the number of integer solutions of $x^2-Ny^2=1$ is infinite May 3 reviewed Leave Closed What are some examples of notation that really improved mathematics? May 3 reviewed Looks OK Holomorphic function injective on annulus => injective on unit disk? May 3 reviewed Delete Basic probability - either event occurs but not both May 3 reviewed Looks OK Adding rows to calculate the determinant. May 3 answered Any finite index subgroup of $\mathbb Z_p$ is open May 3 comment Is every point in the set defining some curve or line in $\mathbb{C}$ or $\mathbb{R}$ a boundary point? Instead of "finitely many zeroes" it may also happen that $f(g(t))$ is identically zero. However, if $f$ is not identically zero, you can pick a point $x_0$ with $f(x_0)\ne 0$ and let $L$ be the line throuh $x_0$ and $x$ May 3 reviewed Leave Open Prove multivariable function is surjective? May 3 reviewed Close How to prove that $\frac{\ln 12}{\ln 18}$ is irrational witout using the change of base rule? May 3 reviewed Leave Open how to understand the generation of cauchy distribution from uniform distribution? May 3 reviewed Close Can we simplify analysis by getting rid of the uncountable reals?